Boiler or the like



Nov. 25, 1969 K. PREVEL BOILER OR THE LIKE Filed June 5, 1968 INVENTOR. Lao 0K F/606/ United States Patent 3,479,992 BOILER OR THE LIKE Ludo K. Frevel, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed June 3, 1968, Ser. No. 733,977 Int. Cl. F22b 15/00, 37/10 US. Cl. 122-235 8 Claims ABSTRACT OF THE DISCLOSURE In wet bottom boilers or the like the boiler tubes on or adjacent to the boiler flow are surrounded with a spaced apart housing in which the open space between the tubes and housing is filled at least to the extent necessary to cover the tubes, with dense, high melting point particulated material such as monazite sand, for example.

Such a structure prevents localized overheating, weakening, and eventual rupturing of the boiler tubes by preventing molten iron, iron sulfide or other molten, heavy substances present in molten slag from contacting the boiler tubes.

Background of the invention This invention relates to apparatus wherein metal tubes are contacted by fused, flowable heated materials, and particularly to so-called wet-bottom boilers.

In so-called wet-bottom boilers the tubes along the floor of the boiler are contacted by molten slage which is withdrawn from the floor atone or more points.

It has been found that the iron-aluminum silicate part of the slag in the boiler also contains heavier substances such as molten iron and iron sulfide which tend to sink to the bottom of the molten slag and contact the boiler tubes. It is believed that the puddles of highly active molten iron and heavy iron sulfide tend to cause localized overheating of boiler tubes which eventually weaken boiler tubes to the point where rupturing of the tubes occurs.

Accordingly, a principal object of this invention is to provide improved boiler apparatus having means for preventing molten slag from contacting boiler tubes.

Another object of this invention is to provide an improved, safer wet bottom boiler.

In accordance with this invention the tubes on the floor of a socalled wet bottom boiler are surrounded by a spaced apart housing, usually made of metal, in which the open space between the boiler tube and its housing is filled, at least to the extent of completely covering the boiler tube with a dense, high melting point particulated material such as monazite sand, for example.

The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawings, in which:

FIG. 1 is a simplified fragmentary diagrammatical view of a wet bottom boiler;

FIG. 2 is a transverse sectional view of a boiler tube assembly in accordance with this invention;

FIG. 3 is a side elevational view, in section, of the boiler tube assembly of FIG. 2;

FIG. 4 is a transverse sectional view of an alternative boiler tube assembly in accordance with this invention; and

3,479,992 Patented Nov. 25, 1969 FIG. 5 is a side elevational view, in section, of the boiler tube assembly shown in FIG. 4.

Referring to the drawing, and particularly to FIG. 1, there is shown a representation of a boiler tube assembly composed of arrays 10, 12 of vertically disposed boiler tubes, a header 14, and an array of tubes 16 along the floor of a boiler. The array 16 slopes downwardly toward a slag discharge tube 18 disposed usually in the central section of the floor of the furnace.

Usually, when an array of boiler tubes is installed, a layer of chromite ore is disposed above and about the boiler tubes to isolate the tubes from molten slag. However, during operation of the boiler, the chrome ore appears to be leached away by the molten slag at a fairly rapid rate. Further, the chromite ore is apparently wet by molten iron and/ or iron sulfide, so those materials may flow through the ore and contact the boiler tubes.

Referring now to FIGS. 2 and 3, there is shown a boiler tube 20 which is surrounded by a slotted tubular element 22 which is coupled to a base or floor plate 24. The element 22 is maintained spaced from the tube 20 by means of annualr spacer elements 30.

The open space between the tubes 20 and the tubular elements 22 is at least substantially filled with dense high melting point particulated material such as monazite sand. The open part at the top of the element 22 is closed by a strip 26 which is tacked to the element 22 at intervals.

An alternative embodiment of the invention is shown in FIGS. 4 and 5. The boiler tube 20a is disposed within a slotted tubular element 22a, but may contact the element 22a along its lower part adjacent to the floor plate 24a.v

Spacer elements 30a along the length of the tube assembly maintain the tube 20a in position. As in the embodiment of FIGS. 2 and 3, the open space between the tubes 20a and elements 22a is at least substantially filled with dense high melting point particulated material such lar hot, dense material settles through the slag bed over the boiler tube assemblies, localized overheating of the tubes 20 or 2011 is prevented by the outer tubular element and the particulated material 28 or 2811. The tubu lar elements 22 or 22a are not under pressure, so cannot explode even if eventually they become perforated. The particulated material is not wet, in any event, by molten iron or iron sulfide, and thus will protect the boiler tubes as monazite sand. A capping strip 26a, tacked at intervals to the element 22a, closes the slot in the element 22a.

In operation, even if molten iron, iron sulfide or simi- 20 or 20a even though the elements 22 or 22a eventually become perforated.

What is claimed is:

1. A heat exchange floor assembly comprising an array of heat exchange tubes, a housing member larger in diameter than the diameter of a tube with which it is associated, each housing member surrounding a heat exchange tube, means for maintaining said housing member in predetermined spatial relationship with respect to said tube, the open annulus between said tube and said housing member being substantially filled with a dense, particulated high melting point material.

2. An assembly in accordance with claim 1, wherein said tubes are surrounded by said housing members along that part of the tube subject to contact by molten materials.

3 4 3. An assembly in accordance with claim 1, wherein 8. An assembly in accordance with claim 1, wherein said assembly is part of the floor of a Wet bottom boiler. means are provided for venting gases from said annulus.

4. An assembly in accordance with claim 1, wherein said housing is generally equally spaced from said tube. References Cit d 5. An assembly in accordance with claim 1, wherein said dense particulated material is monazite sand.

UNITED STATES PATENTS 6. An assembly in accordance with claim 1, wherein 1,8 5,93 1931 Bell 122-235 said molten material is a slag which contains molten iron ,2 6 2 193 Bros 122-6 or iron sulfide and said tubes and housing members are 2, 8, 8 2/1939 Lucke 122235 made of steel. 10

7. An assembly in accordance with claim 1, wherein KENNETH W. SPRAGUE, Primary Examiner said housing members are slotted and have a closure section secured thereto.

5% UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3, 79,99 Dated November 25, 1969 Patent No.

Inventor(s) L. K. Frevel It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 2, line 22, change "annualr" to read --annular--; delete lines 38 through &5; after line &8, insert --lar hot, dense material settles through the slag bed over the boiler tube assemblies, localized overheating of the tubes 20 or 208. is prevented by the outer tubular element and the particulated material 28 or 28a.

The tubular elements 22 or 228. are not under pressure, so cannot explode even if eventually they become perforated. The particulated material is not wet, in any event, by molten iron or iron sulfide, and thus will protect the boiler tubes--.

SIGNED AN'D SEALED JUN 161970 (SEAL) Attest:

Edwin-Flew! WILLIAM E. susurnER.

Commissioner of Paton L. Officer 

